Mobile display size
300x50 — Mobile Banner
Also called Small mobile banner.
- Width
- 300px
- Height
- 50px
- Aspect ratio
- 6:1
- Area
- 15,000px²
Actual size
Rendered at true pixel dimensions. On a narrow screen it scales down to fit.
Where it runs
Mobile inline or anchored positions on narrow viewports.
Why it is used
A slightly narrower mobile banner for viewports where a full 320 pixels does not fit once the layout's own padding is accounted for. It predates the near-universal 320-pixel minimum viewport and mostly persists in older in-app SDK integrations.
What to watch for
Considerably less demand than 320x50 for the sake of 20 pixels, so a slot restricted to this size will fill noticeably worse. Almost every placement should simply accept both and let the auction decide.
File weight for standard display is commonly specified at around 150 KB initial load, but publisher specs vary and the figure that governs is always the one written into the insertion order. Check it before trafficking rather than after a creative is rejected.
Related sizes
Dimensions follow IAB Tech Lab display guidelines. Placement and performance guidance is practitioner knowledge, last verified July 2026.